US11841304B1ActiveUtilityPatentIndex 70
Device and method for testing effective diffusion coefficient of helium in helium-bearing natural gas
Est. expiryNov 23, 2042(~16.4 yrs left)· nominal 20-yr term from priority
G01N 13/00G01N 30/88G01N 2013/003G01N 1/00G01N 2203/0256G01N 33/24G01N 33/0052G01N 33/0016
70
PatentIndex Score
3
Cited by
9
References
9
Claims
Abstract
A device and method for testing an effective diffusion coefficient of helium in helium-bearing natural gas solves the problem that there is currently no systematic method or supporting experimental device to quantitatively characterize the diffusion behavior of helium in helium-bearing natural gas. The device includes a diffusion system and a gas sampling and analysis system. The diffusion system includes an upstream diffusion chamber, a downstream diffusion chamber, and a true triaxial apparatus, and is configured to simulate a gas diffusion process. The gas sampling and analysis system includes an upstream gas sample retention chamber, a downstream gas sample retention chamber, and a chromatographic analyzer, and is configured to sample a diffusing gas and analyze composition of the gas. By performing diffusion process simulation, gas sampling and analysis, and data calculation and fitting, the effective diffusion coefficient of helium in the helium-bearing natural gas is finally acquired.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1. A device for testing an effective diffusion coefficient of helium in helium-bearing natural gas, comprising:
a diffusion system and a gas sampling and analysis system, wherein
the diffusion system comprises an upstream diffusion chamber, a downstream diffusion chamber, and a true triaxial apparatus; and two ends of the true triaxial apparatus are respectively connected to the upstream diffusion chamber and the downstream diffusion chamber;
the upstream diffusion chamber is filled with argon, and the downstream diffusion chamber is filled with helium-bearing natural gas for simulating an actual environment; and the true triaxial apparatus is configured to accommodate a rock core, apply a load to the rock core, and simulate a formation temperature;
the gas sampling and analysis system comprises an upstream gas sample retention chamber, a downstream gas sample retention chamber, and a chromatographic analyzer;
the upstream gas sample retention chamber is connected to the upstream diffusion chamber to sample the gas in the upstream diffusion chamber; and the downstream gas sample retention chamber is connected to the downstream diffusion chamber to sample the gas in the downstream diffusion chamber;
an initial state of the upstream gas sample retention chamber and the downstream gas sample retention chamber is a vacuum state for convenience of gas sampling;
the chromatographic analyzer is configured to analyze gas composition in the upstream gas sample retention chamber and the downstream gas sample retention chamber;
the true triaxial apparatus comprises pressure plates, sealing strips, a pressure block, a pressure chamber, a hydraulic cylinder, and a hydraulic bag;
the pressure plates are provided inside the pressure chamber, and the pressure plates are abutted against the rock core to apply a pressure to the rock core;
adjacent pressure plates are separated by the sealing strip; and the pressure plates and the sealing strips enclose a rock core accommodation chamber;
the pressure block comprises a first end connected to the pressure plate and a second end connected to the hydraulic bag; and the hydraulic bag is expanded to push the pressure block to move towards the rock core;
the pressure block comprises the first end connected to the pressure plate and the second end connected to the hydraulic cylinder;
the hydraulic bag is a hollow cylindrical structure with a rectangular axial section, and the hydraulic bag is embedded in the pressure chamber; and the hydraulic bag is provided between the pressure block and the pressure chamber;
each of the sealing strips comprises an arc segment, a positioning segment, and a reinforced sealing segment; the arc segment comprises a front end surface connected to the reinforced sealing segment and a rear end surface connected to the positioning segment; and the arc segment, the positioning segment, and the reinforced sealing segment are distributed coaxially;
a plurality of ellipsoidal deformation cavities parallel to an axis of the sealing strip are uniformly distributed inside the arc segment, the positioning segment, and the reinforced sealing segment; and at least two ellipsoidal deformation cavities perpendicular to the axis of the sealing strip are arranged at each of a connection position between a first end of the arc segment and the positioning segment and a connection position between a second end of the arc segment and the reinforced sealing segment;
the upstream diffusion chamber is structurally identical to the downstream diffusion chamber, and the upstream diffusion chamber comprises a gas storage cylinder and a distribution tube;
the upstream gas sample retention chamber is structurally identical to the downstream gas sample retention chamber, and the upstream gas sample retention chamber comprises a gas bearing and storage tank, a piston member, and a driving airbag; the piston member is embedded in the gas bearing and storage tank and slidably connected to an inner side of the gas bearing and storage tank; the piston member is coaxial with the gas bearing and storage tank, and the piston member divides the gas bearing and storage tank into a helium buffer chamber and a regulating chamber along an axial direction; and the driving airbag is embedded in the regulating chamber, and the driving airbag pushes the piston member to adjust a size of the helium buffer chamber; and
the diffusion system further comprises a differential pressure sensor; and two ends of the differential pressure sensor are respectively connected to the upstream diffusion chamber and the downstream diffusion chamber to detect a gas pressure difference between the upstream diffusion chamber and the downstream diffusion chamber.
2. The device for testing the effective diffusion coefficient of helium in helium-bearing natural gas according to claim 1 , further comprising a pressure difference balancing argon cylinder and an environmental simulation gas supply cylinder, wherein
the pressure difference balancing argon cylinder is connected to the upstream diffusion chamber to inject the argon into the upstream diffusion chamber; and
the environmental simulation gas supply cylinder is connected to the downstream diffusion chamber to inject the helium-bearing natural gas for simulating the actual environment into the downstream diffusion chamber.
3. The device for testing the effective diffusion coefficient of helium in helium-bearing natural gas according to claim 2 , wherein the diffusion system further comprises a transfer tube and a first control valve;
the transfer tube is connected in parallel with the differential pressure sensor; and two ends of the transfer tube are respectively connected to the upstream diffusion chamber and the downstream diffusion chamber; and
the first control valve is provided on the transfer tube to control switching-on/off of the transfer tube.
4. The device for testing the effective diffusion coefficient of helium in helium-bearing natural gas according to claim 3 , further comprising a second control valve and a third control valve, wherein
the second control valve is provided between the upstream diffusion chamber and the upstream gas sample retention chamber to control switching-on/off of the upstream diffusion chamber and the upstream gas sample retention chamber; and
the third control valve is provided between the downstream diffusion chamber and the downstream gas sample retention chamber to control switching-on/off of the downstream diffusion chamber and the downstream gas sample retention chamber.
5. The device for testing the effective diffusion coefficient of helium in helium-bearing natural gas according to claim 4 , further comprising a vacuum pump, wherein the vacuum pump is connected to the diffusion system and the gas sampling and analysis system to vacuumize the diffusion system, the gas sampling and analysis system, and a connecting tube.
6. The device for testing the effective diffusion coefficient of helium in helium-bearing natural gas according to claim 5 , wherein the true triaxial apparatus further comprises an electric heating wire; and
the electric heating wire is provided at a side of the pressure plate to adjust a temperature of the rock core, wherein the side of the pressure plate is away from the rock core.
7. The device for testing the effective diffusion coefficient of helium in helium-bearing natural gas according to claim 6 , further comprising a first booster pump, wherein
the first booster pump is connected to the hydraulic bag to drive the hydraulic bag to expand, so as to push the pressure block to move towards the rock core.
8. The device for testing the effective diffusion coefficient of helium in helium-bearing natural gas according to claim 7 , wherein the gas sampling and analysis system further comprises a chromatographic carrier gas cylinder; and the chromatographic carrier gas cylinder is connected to the upstream gas sample retention chamber, the downstream gas sample retention chamber and the chromatographic analyzer to carry the gas in the upstream gas sample retention chamber and the gas in the downstream gas sample retention chamber into the chromatographic analyzer.
9. A method for testing an effective diffusion coefficient of helium in helium-bearing natural gas, using the device for testing the effective diffusion coefficient of helium in helium-bearing natural gas according to claim 8 , and comprising the following steps:
rock core loading: putting the rock core into the true triaxial apparatus; applying a pressure, and maintaining the pressure; and adjusting a temperature of the rock core to a test temperature, and keeping the temperature constant;
vacuumizing: starting the vacuum pump to vacuumize the diffusion system, the gas sampling and analysis system, and the connecting tube;
gas injection: opening the pressure difference balancing argon cylinder to inject the argon into the upstream diffusion chamber; opening the environmental simulation gas supply cylinder to inject the helium-bearing natural gas for simulating the actual environment into the downstream diffusion chamber; and closing the pressure difference balancing argon cylinder and the environmental simulation gas supply cylinder when a gas pressure in the upstream diffusion chamber and a gas pressure in the downstream diffusion chamber reach a preset value;
gas diffusion: communicating the upstream diffusion chamber, the downstream diffusion chamber, and the true triaxial apparatus; and allowing, under an action of a concentration gradient, the argon in the upstream diffusion chamber to diffuse through the rock core to the downstream diffusion chamber and the helium-bearing natural gas in the downstream diffusion chamber to diffuse through the rock core to the upstream diffusion chamber;
gas sampling and analysis: turning, during a diffusion process, the vacuum pump on to vacuumize the upstream gas sample retention chamber and the downstream gas sample retention chamber, and then turning the vacuum pump off; turning the second control valve on to allow the gas in the upstream diffusion chamber to enter the upstream gas sample retention chamber, and turning the third control valve on to allow the gas in the downstream diffusion chamber to enter the downstream gas sample retention chamber; then, turning the second control valve and the third control valve off; analyzing, through the chromatographic analyzer, compositions of a mixed gas in the upstream gas sample retention chamber and compositions of the mixed gas in the downstream gas sample retention chamber, respectively; and repeating this step at least five times to acquire at least five groups of data on the compositions of the mixed gas, wherein the data, acquired at last two times, on the compositions of the mixed gas are identical; and
diffusion coefficient calculation: calculating, according to Fick's second law, an effective diffusion coefficient D i of an i-th gas in the helium-bearing natural gas as follows:
D
i
=
a
L
A
(
1
1
/
V
upstream
+
1
/
V
downstream
)
,
(
1
)
wherein,
L denotes a length of the rock core;
A denotes a cross-sectional area of the rock core;
V upstream denotes a volume of the upstream diffusion chamber;
V downstream denotes a volume of the downstream diffusion chamber;
α denotes a concentration decline index of the i-th gas, and α is calculated as follows:
a
=
ln
(
Δ
C
0
Δ
C
t
)
/
Δ
t
,
(
2
)
wherein, ΔC 0 denotes a concentration difference of the i-th gas in the upstream diffusion chamber and the downstream diffusion chamber at an initial time t 0 during the diffusion process;
AC, denotes a concentration difference of the i-th gas in the upstream diffusion chamber and the downstream diffusion chamber at a time t during the diffusion process; and
At denotes a diffusion time, Δt=t−t 0 ;
in the diffusion process, a natural logarithm of a ratio of the concentration difference at the initial time t 0 to the concentration difference at the time t is linear with the diffusion time Δt;
therefore, according to equations (1) and (2),
ln
(
Δ
C
0
Δ
C
t
)
=
D
i
E
t
-
D
i
E
t
0
,
(
3
)
wherein, E=A(1/V upstream +1/V downstream )/L is a constant.
according to equation (3), a slope k is acquired by fitting through a least squares method; and
finally, the effective diffusion coefficient of the i-th gas in the helium-bearing natural gas is D i =k/E.Cited by (0)
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